1. Field of the Invention
The present invention relates to a flashlight using a light emitting diode (hereinafter, referred to as LED) as a lamp (hereinafter, referred to as LED flashlight), and more particularly to an LED flashlight having an improved LED lamp module.
2. Description of the Related Art
Recently, as a semiconductor technology makes great strides, high-luminance LED devices and flashlights using the high-luminance LED devices as a lamp have been variously developed and produced on a commercial scale.
Generally, the LED has a life span about 100,000 hours, which is remarkably longer than the life span of a filament bulb or a discharging lamp, to thereby allow the LED to be semi-permanently used. In addition, since the LED is operated with very low power, the LED can keep longer that the filament bulb.
Generally, the LED flashlight may use one LED or a plurality of LED. According to a conventional structure of the LED flashlight using one LED, lead wires of the LED are inserted into a lamp holder and extended rearwards. Then, the extended lead wires are bent and electrically connected to a positive or a negative electrode of a battery by a switching operation. However, the conventional LED flashlight requires a great number of parts for connecting the electrodes and the lead wires, so an assembling process thereof is very complicated.
According to a conventional structure of the LED flashlight using a plurality of LED, the LEDs are used as a lamp of a head flash. The head flash radiates a white-light by combining red, yellow, and blue LEDs.
Since forward voltage and current of the LED generally drop as a temperature of a junction part of the LED is increased, a luminance of the LED is lowered as the temperature increases. Intensity of current passing through high-luminance LEDs is higher than intensity of current passing through conventional LEDs, so heat is generated when using the high-luminance LEDs for a long time. Therefore, an ambient temperature of the high-luminance LEDs is increased together with the temperature of the junction part due to the heat, so luminance of the high-luminance LEDs is gradually lowered.
In addition, since the LED used as a lamp of the flashlight is installed in a closed space of a head section of the flashlight and is shielded from external air, the ambient temperature of the LED is rapidly increased due to a thermal resistance of the LED.
In extreme cases, the characteristic of the LED is varied due to thermal stress applied to the LED, thereby shortening the life span of the LED and causing a trouble of the LED.
Therefore, a usage data book of the LED recommends a user to use the LED below maximum rated voltage and maximum rated current thereof. However, in case that the LED is installed in the closed space of the head section of the flashlight, heat generated from the LED still remains as a problem.
In addition, even if the LED is operated below maximum rated voltage and maximum rated current thereof, driving voltage of the LED is limited below rated voltage in use so luminance of the flashlight is limited below a predetermined level.
Accordingly, dealing of heat generated from the LED is seriously considered when designing the flashlight using the LED as a lamp to achieve uniform luminance even if the flashlight is used for a long time.